When two or more cables such as telecommunications cables are spliced together, the splice area is ordinarily housed within a protective cover known as a closure. Such closures often have included cylindrical covers with one or more longitudinal joints and end blocks that surround incoming and outgoing cables and that form seals with the covers. An example of a prior art closure is shown in U.S. Pat. No. 3,636,241 which issued on Jan. 18, 1972 in the names of R. B. Baumgartner et al. Closures which are effective in providing protection for the splice connections are available in the marketplace, but in many instances their assembly is relatively time consuming, often requiring specialized tools and equipment which in a limited space such as a narrow trench are difficult to handle and operate. Also, because of the number of different size cables in the field, a user must inventory a corresponding number of different size closures.
Common to substantially all closures is the requirement that they restrict moisture ingress. The integrity of systems which are used to restrict moisture ingress is important especially because of transmission parameters which are readily affected by changes in the moisture content within the cable. Water can enter a splice area through an enclosure imperfection or through one of the cables, in the latter case travelling from a point of damaged cable sheathing, along the conductor core, to the connections between the spliced conductors.
Various systems are used in available closures for providing a waterproof closure. To prevent the ingress of moisture, some systems employ dry air, nitrogen or a similar chemically inert gas in the cables and closures. In this type of closure, the gas is pressurized to create a flow from enclosed equipment through any openings and prevent the ingress of moisture. In the recent past, closures have been filled with a curable, liquid encapsulant to provide moisture protection or sealed in ways other than with pressurized gas. For example, another commonly used closure includes a heat shrinkable sleeve.
Not infrequently, due to line failure or routine maintenance, one or more newly installed cables must be joined or some of the conductors are rejoined to others. Thus the reentry of and the effective resealing of the closure becomes necessary. Accordingly, the reentry of the closure and its resealing should be made as easy as possible. The reentry of some prior art closures that are filled with a waterproofing material is a time-consuming task for a craftperson.
In one prior art system, a plastic liner is placed around the splice area and secured to the cables, thereby forming an enclosure into which liquid encapsulant is poured. The encapsulant, which is at ambient pressure, flows to displace most of the air within the closure, but, being relatively viscous, does not penetrate far, if at all, into the end portions of the cables. The encapsulant in the closure is pressurized to some degree by wrapping ties, tape or the like, around the closure. In such a system, any encapsulant volume change subsequent to the wrapping leads to a change in pressure. These shortcomings tend to impair the effectiveness of the encapsulant in protecting the connections between the spliced conductors from moisture.
In application Ser. No. 619,266 filed on June 11, 1984, in the names of F. J. Mullin and W. C. Reed, a sheet of an elastomeric material in the form of a bladder is adapted to envelop spliced conductors, and to provide containment for a liquid encapsulant at a pressure that is substantially greater than ambient pressure. The bladder is enclosed in a substantially rigid enclosure, which serves to protect the bladder as well as to limit the expansion of the bladder under pressure. Filling the bladder with liquid encapsulant and controlling the pressurizing of the encapsulant ensures the formation of a substantial layer of encapsulant between the spliced conductors and the walls of the bladder, and urges encapsulant into voids and for some distance into the cable core at each end of the closure. Should enough encapsulant penetrate into the cables to cause a drop of pressure within the containment bladder, additional encapsulant can be pumped into the bladder, thereby increasing the pressure again to the desired level, and restoring encapsulant to a volumetric level which is sufficient to protect the splice connections.
The containment facilities in the above-disclosed application are adapted to maintain the pressure for a time sufficient for at least a part of the encapsulant to solidify. The arrangement results in the provision of an effective gasket because the encapsulant cures while pressurized and under a compressive load. Many cables comprise materials with which it is difficult or impossible to form an adhesive bond. Compressively loaded, cured encapsulant, urged against any surface it contacts, resists water intrusion along surfaces with which the encapsulant does not form an adhesive bond.
Although the just-described system is an improvement over prior art systems, provisions are needed for an easy-to-assemble closure which includes the containment bladder. Inasmuch as encapsulation is widely used to waterproof closures, especially in the telecommunications industry, a system that is convenient, reenterable, economical and effective in protecting splice connections from moisture to prevent transmission faults would be of considerable interest. Further, the sought-after closure desirably should include facilities for isolating the splice connections from the cable core along which water ingresses the closure.
What is needed and what the prior art seemingly does not include is an easily assembled, reenterable closure adapted to receive an encapsulant. The closure should comprise a relatively small number of components and be assembled easily about splice connections involving different size distribution cables and buried service cables. Such a closure is desirable where future changes will be required in splice connections. It does not appear that the prior art includes such a relatively inexpensive, reliable closure which is assembled readily in the field and which includes provisions for the controlled pressurization of the encapsulant.